The problem here is attribute syntax 'caseIgnoreString' vs 'caseIgnoreIA5String'. The above can happen when an attempt is made to insert a null/blank character to an attribute while the syntax type of that attribute is 'caseIgnoreString'. Due to strict x500 standards, CA Directory doesn't allow that. If you must, you can change the syntax to 'caseIgnoreIA5String'.
NOTE: Modifying any CA Directory product provided schema file is not supported. Use it at your own risk. Good idea to create your own extended schema and use that as your business requirement.